Add: tab monitor

src/background.js

@@ -4,6 +4,7 @@ import browser from "webextension-polyfill";
 
 import {pref} from "./lib/pref.js";
 import {createTab} from "./lib/tab.js";
+import {tabMonitor} from "./lib/tab-monitor.js";
 import {fetchImage} from "./lib/fetch-image.js";
 import {download} from "./lib/downloader.js";
 import {imageCache} from "./lib/image-cache.js";
@@ -143,7 +144,7 @@ const MENU_OPTIONS = [
 			handler(tab, info.frameId);
 		},
 		contexts: ["page", "image"],
-		oncontext: () => pref.get("contextMenu")
+		oncontext: () => pref.get("contextMenu") && !tabMonitor.isExtensionPage()
 	}))
 ];
 
@@ -166,6 +167,7 @@ if (menus) {
       }
     });
   });
+  tabMonitor.on("change", () => menus.update());
 }
 
 // setup dynamic icon

src/lib/tab-monitor.js

@@ -0,0 +1,53 @@
+// observee the latest active tab
+import browser from "webextension-polyfill";
+import EventLite from "event-lite";
+
+class TabMonitor extends EventLite {
+  constructor() {
+    super();
+    this._tab = null;
+    this._onActivated = this._onActivated.bind(this);
+    // FIXME: make it work with multiple windows
+    browser.tabs.onActivated.addListener(this._onActivated.bind(this));
+    browser.tabs.onUpdated.addListener(this._onUpdated.bind(this), {properties: ["url"]});
+  }
+
+  async _onActivated({tabId}) {
+    // FIXME: 
+    this._tab = await browser.tabs.get(tabId);
+    this.emit("change");
+  }
+
+  _onUpdated(tabId, changeInfo, tab) {
+    if (!this._tab) {
+      return;
+    }
+    if (tabId === this._tab.id) {
+      this._tab = tab;
+      this.emit("change");
+    }
+  }
+
+  getTab() {
+    // if (!this._tab) {
+    //   const tabs = await browser.tabs.query({active: true, currentWindow: true});
+    //   this._tab = tabs[0];
+    // }
+    return this._tab;
+  }
+
+  destroy() {
+    browser.tabs.onActivated.removeListener(this._onActivated);
+    browser.tabs.onUpdated.removeListener(this._onUpdated);
+  }
+
+  isExtensionPage() {
+    if (!this._tab) {
+      return false;
+    }
+    return this._tab.url.startsWith(browser.runtime.getURL(""));
+  }
+
+}
+
+export const tabMonitor = new TabMonitor();